432 CRUSTACEA. 



Tliii> oxtraordiDary p:r'ni.is has been considered as affording- proof of the rclntion of llio Tiiinliitcs to the Isiopodous 

 Ci'i.istacca, tlic Ijody being- divided into three long-itudinal portions, as in tlmsc fussjls. 'i'lii; l;-ciiiis has latel-y been 

 described and (iLriired in detail by Eights, under the name oi Brovgniai tin Tiihihiloidi's, in tiie Transactions of iha 

 Allxuni Jn.stifNtr.] 



1(1 the olbri (.['/u/oif/odda the evos are lateral, and not placed upon tubercIeFi, ami the tail is composed of four or 

 six joints; of tliesc the majority have the eyes nut formed of granular ocelli; the autennie are at least seven- 

 joiiiteri, and the six fore-lcLfS terminated by a strong hook ; of these the foUo^ving- subgenera have the tail always 

 six-Jointed, and the lower antennte never exceed in length half of the body. 



Ciimuthoa, Fab., having tlie mandibles not exposed, the antennje of nearly eipial lenglli, the eyes slightly appa- 

 rent, and the terminal joint of the tail transverse-quadrate. Type, Ciiinothoa 0-2.s1ruin, Tab. [These animals \vere 

 well known to the ancients, who gave them the name of (Esiriis and As'dns, from the resemblance between their 

 habits and those of the breeze-tiies. Aristotle says of the species above mentioned, " Fishes are attacked by a 

 sea-louse, which is not produced from the lisli but from the mud/'] 



Ir/it/ii/op/ii/us, Latr. {Nerodlaand Lironecn, Leach,) differs fi-om the last in having the terminal segment of the 

 tail nearly triangular. To these succeed various subgenera, instituted by Leach upon sti-uctura! characters, such 

 as the relative length of the antennae, form of the swimming plates of the tail, &c. 



In CEofl, and several others, the eyes are generally large, and converge anteriorly. 



Si/noditi:, Latr., having also six segments to the tail, differs from all the preceding in tiie large size of its 

 exserted mandibles. 



ClrolunOy Leacli, and several others, have only five segments in tlic tail, and the !en:::tli of the inferior antennae 

 is greater than tliat of half the body. 



Eun/dicc, Leach, belonging to this division, naturally conducts us in the granular >trHrtnrf of its eyes to 



Limnor'ia, Leach, in which these organs resemble numerous ocelli, placed close togi't I n.-r, which Iia\e the antenna; 

 inserted in a line, and not composed of more than four joints, and all the legs are formed fur walking. The tail is 6- 

 jointed, tlie terminal joint being large and suborbicular. The only known (recent) species \?,V[i(t L. terebrans, Leach, 

 wdiich, although not more than a sixth of an inch in length, is, in its powers of multiplication, exceedingly destruc- 

 tive. It pierces the wood of vessels in different directions with astonishing alacrity, and contracts itself into a 

 ball when alarmed. It is found in different parts of the British Ocean, [atfacking piles of wood immersed in the 

 v;atcr ill our dockyards, flood-gates, timber-bridges, chain-piers, &c., and which it perforates in a most alarming 

 manner. The boring of the insect having for its object the procuring of food, the contents of its stomach resem- 

 ble comminuted wood. It is necessary that the hole in which it is at work should be -filled with salt water. 

 Coating the wood with copper-headed naUs, and the use of Kyanized wood, have been suggested as remedies against 

 its attfick>.]. 



Professor Germar forwarded to Dejean the tignre and description of a small fossil crnstaccous animal, -which 

 appears to us to belong to this subgenus. 



The third section, Sphjeromides, Latr., exhibits four distinct, ami sctaceons or conical antenntc, ter- 

 minated (except in Anlhnrd) by a multiarticulate Ulamcnt : tlic. lower pair is always the longest, and 

 inserted beneath tlic lia^al joint of the upper, \^hicll is tliick and broad. The mouth is of the o^diuar^' 

 f(irni. Tlif: br.tnchjrc are vesicular or soft, naked, and disposed longitudinally in pairs. The tail is only 

 composed of two complete and moveable segments, the first of wliich, however, exhibits impressed 

 and transverse lines, indicating the vestiges of the same nundier of segments. On each side of the pos- 

 terior cxtrcniity of the liody is a swimmeret, terminated by two plates, of \\liich the inferior alone is 

 moveable, and the upper is formed by an external elongation of the common sii]iport. The liranchial 

 appendages are curved inwards ; the inner side of t!ie anlci-ior pair is accompanied in the males with a 

 small linear and elongated piece. The anterior part of the head, situated beneath tlie antcnna\ is 

 triangular, or in the shape of a heart reversed. Tiie majority have the body oval or oblong, assuming 

 the form of a ball when contracted. 



Zuznra, Leach (with very large swimmerets), and Spharoma, Latr. (with moderate sized-swimmerets). have the 

 impressed lines on the basal segments of the tail not extended to the sides. In the following they extend to Che 

 margin, forming as many incisions, and the basal joint of the antennae forms a long square or linear plate. 



Na-so and Campecopa!a, Leach, have the sixth segment of the body considerably longer than the preceding, 

 whilst it is of equal size in 



Cilicu-a, Leach, Ci/modocea, Leach, ami Di/nanieue, Leach, distinguished by variations in the form of the 

 swimmeret and the sixth segment of the body. 



ji?;//(;(r/T, Leach, differs from all the preceding in its vermiform body, and in having the anteunns scarcely as 

 long as the head, and 4-jointfd. The plates of the swimmeret form a kind of cajisule. {Onjsci/s gracilis, Slon- 

 taguc) 



In the fourtli section, iDOTEiDiiis, Leach, the antcnntc are also four in luimbrr, but phu'cd in the 

 same transvei-se and horizontal line ; the lateral ones are tenninated by a iniiltiartlcnlalc and gnuUially 

 attenuated lilanicnt, the intermediate short, liliform, or sliL;htly thickencil at the tip, and -J-jninted, 

 iiojip of ihc joints being articulated. The mouth is composed of the .same iiai'is as in the preceding. 



